Until very recently, people still used the same principal that Newton had proposed, to derive latitude from the angle of the sun or stars at known times. The sextant (or originally octant) allowed people to do this relative to the horizon, rather than the instrument itself.

Later versions of the sextant included a very simple version for emergency use, called the Bris sextant (not a great name for a device to be used on a rolling ship) and until the advent of GPS systems, bubble sextants were used on aircraft.